This mandrel uses a .125" keyway and accepts one 1.00" bore by 1.00" wide pulley.
The mandrel assm. includes the mandrel, 1/2" mandrel bolt, as well as the mandrel hat washer. The crank bolt must be drilled and tapped 1/2-20" in the head to accept the drive mandrel.
RBS can supply the crank bolt for 7/16", 1/2" and 3/4" threads.